The production of glass fibers by means of a rotary process is well know. In general, molten glass is fed into the spinner which revolves at high speeds. The spinner has a solid lower surface and a peripheral wall containing a multiplicity of orificies. The glass is passed by centrifugal force through the orifices of the peripheral wall in the form of small diameter streams. Positioned circumferentially about the spinner is an annular blower. The blower typically comprised an annular manifold and a discontinuous slot or series of slots for directing a plurality of gaseous jets from the manifold in a downward column or circumferential array. Usually the blowers are supplied with attenuating air by a compressor. The gases discharged from the blower have a pulling effect on the fibers being centrifuged, and the gases serve to attenuate the fiber to its final small diameter.
In a typical blower construction, the discontinuous slot is comprised of downwardly directed openings communicating with the manifold. These openings typically have a square cross section, being, for example, 0.02 inches by 0.02 inches. Also, the lands or blower fins between the openings are typically of the same cross-sectional dimension, 0.02 inches by 0.02 inches. Typically, the height dimension is about four times the width dimension. The blower slots or openings are invariably oriented generally parallel to the axis of rotation of the spinner, which is usually in the downward direction.
It is generally desirable to produce products of fibrous glass and other mineral fibers having the greatest possible strength properties while using the least amount of glass fibers. In certain heavy density fibrous glass products, having a density within the range of from about 1.5 pounds per cubic foot (pcf) to about 10 pcf, products could be made more cheaply, with less glass and less binder, by using shorter and fatter glass fibers than had been heretofore employed. Such heavy density products for which shorter, fatter fibers would be advantageous are commercial ceiling products and roof deck insulation products. The shorter, fatter fibers are particularly advantageous for commercial roof deck products because of the requirement that the flute span test be met.
Heretofore, efforts to make shorter, fatter fibers for uses in heavy density products have not been successful. Attempts to make fatter fibers have usually resulted in creation of longer rather than shorter fibers. Thus, there is a need for a method for making shorter, fatter fibers.